in January 2020, nobody, including you thought this was going to go as far and as fast as it did. By then, very likely the cat was already out of the bag and a worldwide travel ban would have helped but would not have prevented the pandemic outright. Was this a mistake? Yes, because that decision violates the cautionary principle when dealing with novel diseases. The WHO was concerned with being found to be 'alarmist' but this time around that would have been the right position to take. Ironically had they done so and prevented the pandemic from spreading you would now be berating them for being such idiots that they caused us all to stop traveling for nothing in 2020, on account of the prevention paradox. And that makes you part of the problem: there is nothing that the WHO could have done that in your eyes would have been a proportional response, and when you are dealing with a novel pathogen mistakes are inevitable.

A bit of restraint and some more thinking about this on your part would go a long way towards a more reasonable stance. But those that see the UN and the WHO as the root of all evil tend to do everything they can to avoid seeing reason, instead everything gets bent to the 'UN bad' talking point.

It's the cancelling school (or work) for snow problem in a nutshell.

If you cancel, and there is no snow, you've caused economic damage, which has very real health consequences.

If you don't cancel, and there is heavy snow, you've caused physical damage, with very real health consequences.

Implementing full international pandemic prevention protocols in a timely manner was probably realistically impossible, given it's never been done in the 21st century.

But beyond that, it's questionable whether making the decision at the time, knowing what was known about SARS-CoV-2, was even a justifiable call. For the reasons you mentioned.

And not just because of the alarmist factor, but because of very real (and sometimes lethal) consequences of implementing them. And I don't think there was a case for preemptively being that aggressive, given MERS and SARS-CoV-1 were both regionally contained.